Earn by your blog or website-How to get ads for the blog

I want to know that how we can earn from a blog..How we can get ads on contract basis that we publish on our blog and earn.
I know the ads sites like adsense and others.
Can we get ads from the companies that pays us nice just to display ads...doesn't matter if got clicked or nt.....Is there any site providing this service.
Thanx